here are numerous patents for means to exert a greater force during the eccentric phase of a repetition than during the concentric phase. Potash et. al., in U.S. Pat. No. 5,328,429A, titled: “Asymmetric force applicator attachment for weight stack type of exercise machines,” describes “An attachment for a weight stack type exercise machine to pull the weight stack down while it is being lowered, so that the eccentric exercise force required to lower the stack is greater than the concentric exercise force required to raise it.” Pantolean, in U.S. Pat. No. 5,653,666 A, titled: “Negative resistance weightlifting apparatus,” describes an apparatus which “produces a negative resistance effect by pressing down with an adjustable force on . . . [a] weight as it is being lowered.” Bugallo and Giamba, in U.S. Pat. No. 4,563,003 A, titled: “Weight lifting apparatus having increased force on the return stroke,” describe an apparatus which “has a structure for lifting said weights against said gravity force and lowering said weights under said gravity. A resisting force in addition to said gravity force on the weight is applied to said structure during at least a portion of said downward movement of said weights.”
These and other invention in the field have as their object to produce a greater force during the eccentric phase of an exercise repetition than in the concentric phase by means of some apparatus.
It is also well known that the torque around a joint may vary within the range of motion of the exercise by changes in the moment arm during the range of motion. De Simone (Bill De Simone, 2004, Moment Arm Exercise, Amazon, Spiral-bound) for example, describes such changes in moment arms during exercises.